Acronym for “authentication, authorization, and accounting.” Protocol for authenticating a user based on their verifiable identity, authorizing a user based on their user rights, and accounting for a user’s consumption of network resources.

Also referred to as “merchant bank,” “acquiring bank,” or “acquiring financial institution”. Entity, typically a financial institution, that processes payment card transactions for merchants and is defined by a payment brand as an acquirer. Acquirers are subject to payment brand rules and procedures regarding merchant compliance. See also Payment Processor. .

Elevated or increased privileges granted to an account in order for that account to manage systems, networks and/or applications. Administrative access can be assigned to an individual’s account or a built-in system account. Accounts with administrative access are often referred to as “superuser”, “root”, “administrator”, “admin”, “sysadmin” or “supervisor-state”, depending on the particular operating system and organizational structure.

Program or software capable of detecting, removing, and protecting against various forms of malicious software (also called “malware”) including viruses, worms, Trojans or Trojan horses, spyware, adware, and rootkits.

Acronym for “attestation of compliance.” The AOC is a form for merchants and service providers to attest to the results of a PCI DSS assessment, as documented in the Self-Assessment Questionnaire or Report on Compliance.

Also referred to as “audit trail.” Chronological record of system activities. Provides an independently verifiable trail sufficient to permit reconstruction, review, and examination of sequence of environments and activities surrounding or leading to operation, procedure, or event in a transaction from inception to final results.

In the context of access control, authorization is the granting of access or other rights to a user, program, or process. Authorization defines what an individual or program can do after successful authentication. In the context of a payment card transaction, authorization occurs when a merchant receives transaction approval after the acquirer validates the transaction with the issuer/processor.

Vulnerability that is created from insecure coding methods, where a program overruns the buffer's boundary and writes data to adjacent memory space. Buffer overflows are used by attackers to gain unauthorized access to systems or data.

Also known as Card Validation Code or Value, or Card Security Code. Refers to either: (1) magnetic-stripe data, or (2) printed security features.

Data element on a card's magnetic stripe that uses secure cryptographic processes to protect data integrity on the stripe, and reveals any alteration or counterfeiting. Referred to as CAV, CVC, CVV, or CSC depending on payment card brand. The following list provides the terms for each card brand:

CAV - Card Authentication Value (JCB payment cards)

PAN CVC - Card Validation Code (MasterCard payment cards)

CVV - Card Verification Value (Visa and Discover payment cards)

CSC - Card Security Code (American Express)

For Discover, JCB, MasterCard, and Visa payment cards, the second type of card verification value or code is the rightmost three-digit value printed in the signature panel area on the back of the card. For American Express payment cards, the code is a four-digit unembossed number printed above the PAN on the face of the payment cards. The code is uniquely associated with each individual piece of plastic and ties the PAN to the plastic. The following list provides the terms for each card brand:

At a minimum, cardholder data consists of the full PAN. Cardholder data may also appear in the form of the full PAN plus any of the following: cardholder name, expiration date and/or service code See Sensitive Authentication Data for additional data elements that may be transmitted or processed (but not stored) as part of a payment transaction.

Mobile communications through wireless telephone networks, including but not limited to Global System for Mobile communications (GSM), code division multiple access (CDMA), and General Packet Radio Service (GPRS).

Acronym for Carnegie Mellon University's “Computer Emergency Response Team.” The CERT Program develops and promotes the use of appropriate technology and systems management practices to resist attacks on networked systems, to limit damage, and to ensure continuity of critical services.

Acronym for “Center for Internet Security.” Non-profit enterprise with mission to help organizations reduce the risk of business and e-commerce disruptions resulting from inadequate technical security controls.

Technique or technology (either software or hardware) for encrypting contents of a specific column in a database versus the full contents of the entire database. Alternatively, see Disk Encryption or File-Level Encryption.

Compensating controls may be considered when an entity cannot meet a requirement explicitly as stated, due to legitimate technical or documented business constraints, but has sufficiently mitigated the risk associated with the requirement through implementation of other controls. Compensating controls must: (1) Meet the intent and rigor of the original PCI DSS requirement; (2) Provide a similar level of defense as the original PCI DSS requirement; (3) Be “above and beyond” other PCI DSS requirements (not simply in compliance with other PCI DSS requirements); and (4) Be commensurate with the additional risk imposed by not adhering to the PCI DSS requirement. See “Compensating Controls” Appendices B and C in PCI DSS Requirements and Security Assessment Procedures for guidance on the use of compensating controls.

A system or technology that is deemed by the entity to be of particular importance. For example, a critical system may be essential for the performance of a business operation or for a security function to be maintained. Examples of critical systems often include security systems, public-facing devices and systems, databases, and systems that store, process, or transmit cardholder data. Considerations for determining which specific systems and technologies are critical will depend on an organization’s environment and risk-assessment strategy.

A value that determines the output of an encryption algorithm when transforming plain text to ciphertext. The length of the key generally determines how difficult it will be to decrypt the ciphertext in a given message. See Strong Cryptography.

Discipline of mathematics and computer science concerned with information security, particularly encryption and authentication. In applications and network security, it is a tool for access control, information confidentiality, and integrity.

The time span during which a specific cryptographic key can be used for its defined purpose based on, for example, a defined period of time and/or the amount of cipher-text that has been produced, and according to industry best practices and guidelines (for example, NIST Special Publication 800-57).

Acronym for “Common Vulnerability Scoring System.” A vendor agnostic, industry open standard designed to convey the severity of computer system security vulnerabilities and help determine urgency and priority of response. Refer to ASV Program Guide for more information.

Login account predefined in a system, application, or device to permit initial access when system is first put into service. Additional default accounts may also be generated by the system as part of the installation process.

Password on system administration, user, or service accounts predefined in a system, application, or device; usually associated with default account. Default accounts and passwords are published and well known, and therefore easily guessed.

In the context of PA-DSS, a dependency is a specific software or hardware component (such as a hardware terminal, database, operating system, API, code library, etc.) that is necessary for the payment application to meet PA-DSS requirements.

Technique or technology (either software or hardware) for encrypting all stored data on a device (for example, a hard disk or flash drive). Alternatively, File-Level Encryption or Column-Level Database Encryption is used to encrypt contents of specific files or columns.

Abbreviation for “demilitarized zone.” Physical or logical sub-network that provides an additional layer of security to an organization’s internal private network. The DMZ adds an additional layer of network security between the Internet and an organization’s internal network so that external parties only have direct connections to devices in the DMZ rather than the entire internal network.

Acronym for “domain name system” or “domain name server.” A system that stores information associated with domain names in a distributed database to provide name-resolution services to users on networks such as the Internet.

Process of using two or more separate entities (usually persons) operating in concert to protect sensitive functions or information. Both entities are equally responsible for the physical protection of materials involved in vulnerable transactions. No single person is permitted to access or use the materials (for example, the cryptographic key). For manual key generation, conveyance, loading, storage, and retrieval, dual control requires dividing knowledge of the key among the entities. (See also Split Knowledge).

Process of converting information into an unintelligible form except to holders of a specific cryptographic key. Use of encryption protects information between the encryption process and the decryption process (the inverse of encryption) against unauthorized disclosure. See Strong Cryptography.

Technique or technology under which certain files or logs are monitored to detect if they are modified. When critical files or logs are modified, alerts should be sent to appropriate security personnel.

Hardware and/or software technology that protects network resources from unauthorized access. A firewall permits or denies computer traffic between networks with different security levels based upon a set of rules and other criteria.

Also referred to as “computer forensics.” As it relates to information security, the application of investigative tools and analysis techniques to gather evidence from computer resources to determine the cause of data compromises.

Acronym for “File Transfer Protocol.” Network protocol used to transfer data from one computer to another through a public network such as the Internet. FTP is widely viewed as an insecure protocol because passwords and file contents are sent unprotected and in clear text. FTP can be implemented securely via SSH or other technology. See S-FTP.

Acronym for “General Packet Radio Service.” Mobile data service available to users of GSM mobile phones. Recognized for efficient use of limited bandwidth. Particularly suited for sending and receiving small bursts of data, such as e-mail and web browsing.

Acronym for “Global System for Mobile Communications.” Popular standard for mobile phones and networks. Ubiquity of GSM standard makes international roaming very common between mobile phone operators, enabling subscribers to use their phones in many parts of the world.

Process of rendering cardholder data unreadable by converting data into a fixed-length message digest. Hashing is a one-way (mathematical) function in which a non-secret algorithm takes any arbitrary length message as input and produces a fixed length output (usually called a “hash code” or “message digest”). A hash function should have the following properties: (1) It is computationally infeasible to determine the original input given only the hash code, (2) It is computationally infeasible to find two inputs that give the same hash code. In the context of PCI DSS, hashing must be applied to the entire PAN for the hash code to be considered rendered unreadable. It is recommended that hashed cardholder data include an input variable (for example, a “salt”) to the hashing function to reduce or defeat the effectiveness of pre-computed rainbow table attacks (see Input Variable). For further guidance, refer to industry standards, such as current versions of NIST Special Publications 800-107 and 800-106, Federal Information Processing Standard (FIPS) 180-4 Secure Hash Standard (SHS), and FIPS 202 SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions.

Offers various services to merchants and other service providers. Services range from simple to complex; from shared space on a server to a whole range of “shopping cart” options; from payment applications to connections to payment gateways and processors; and for hosting dedicated to just one customer per server. A hosting provider may be a shared hosting provider, who hosts multiple entities on a single server.

Acronym for “hardware security module” or “host security module.” A physically and logically protected hardware device that provides a secure set of cryptographic services, used for cryptographic key-management functions and/or the decryption of account data.

Acronym for “hypertext transfer protocol over secure socket layer.” Secure HTTP that provides authentication and encrypted communication on the World Wide Web designed for security-sensitive communication such as web-based logins.

Acronym for “intrusion-detection system.” Software or hardware used to identify and alert on network or system anomalies or intrusion attempts. Composed of: sensors that generate security events; a console to monitor events and alerts and control the sensors; and a central engine that records events logged by the sensors in a database. Uses system of rules to generate alerts in response to detected security events. See IPS

Acronym for “Internet Engineering Task Force.” Large, open international community of network designers, operators, vendors, and researchers concerned with evolution of Internet architecture and smooth operation of Internet. The IETF has no formal membership and is open to any interested individual.

Vulnerability that is created from insecure coding techniques resulting in improper input validation, which allows attackers to relay malicious code through a web application to the underlying system. This class of vulnerabilities includes SQL injection, LDAP injection, and XPath injection.

Random data string that is concatenated with source data before a one-way hash function is applied. Input variables can help reduce the effectiveness of rainbow table attacks. See also Hashing and Rainbow Tables.

A protocol, service, or port that introduces security concerns due to the lack of controls over confidentiality and/or integrity. These security concerns include services, protocols, or ports that transmit data or authentication credentials (for example, password/passphrase) in clear-text over the Internet, or that easily allow for exploitation by default or if misconfigured. Examples of insecure services, protocols, or ports include but are not limited to FTP, Telnet, POP3, IMAP, and SNMP v1 and v2.

Acronym for “internet protocol.” Network-layer protocol containing address information and some control information that enables packets to be routed and delivered from the source host to the destination host. IP is the primary network-layer protocol in the Internet protocol suite. See TCP.

Attack technique used to gain unauthorized access to networks or computers. The malicious individual sends deceptive messages to a computer with an IP address indicating that the message is coming from a trusted host.

Entity that issues payment cards or performs, facilitates, or supports issuing services including but not limited to issuing banks and issuing processors. Also referred to as “issuing bank” or “issuing financial institution.”

Abbreviation for “logical partition.” A system of subdividing, or partitioning, a computer's total resources—processors, memory and storage—into smaller units that can run with their own, distinct copy of the operating system and applications. Logical partitioning is typically used to allow the use of different operating systems and applications on a single device. The partitions may or may not be configured to communicate with each other or share some resources of the server, such as network interfaces.

Computers that are designed to handle very large volumes of data input and output and emphasize throughput computing. Mainframes are capable of running multiple operating systems, making it appear like it is operating as multiple computers. Many legacy systems have a mainframe design.

Software or firmware designed to infiltrate or damage a computer system without the owner's knowledge or consent, with the intent of compromising the confidentiality, integrity, or availability of the owner’s data, applications, or operating system. Such software typically enters a network during many business-approved activities, which results in the exploitation of system vulnerabilities. Examples include viruses, worms, Trojans (or Trojan horses), spyware, adware, and rootkits.

In the context of PCI DSS, it is a method of concealing a segment of data when displayed or printed. Masking is used when there is no business requirement to view the entire PAN. Masking relates to protection of PAN when displayed or printed. See Truncation for protection of PAN when stored in files, databases, etc.

For the purposes of the PCI DSS, a merchant is defined as any entity that accepts payment cards bearing the logos of any of the five members of PCI SSC (American Express, Discover, JCB, MasterCard or Visa) as payment for goods and/or services. Note that a merchant that accepts payment cards as payment for goods and/or services can also be a service provider, if the services sold result in storing, processing, or transmitting cardholder data on behalf of other merchants or service providers. For example, an ISP is a merchant that accepts payment cards for monthly billing, but also is a service provider if it hosts merchants as customers.

Method of authenticating a user whereby at least two factors are verified. These factors include something the user has (such as a smart card or dongle), something the user knows (such as a password, passphrase, or PIN) or something the user is or does (such as fingerprints, other forms of biometrics, etc.).

Acronym for “network access control” or “network admission control.” A method of implementing security at the network layer by restricting the availability of network resources to endpoint devices according to a defined security policy.

Acronym for “network address translation.” Also known as network masquerading or IP masquerading. Change of an IP address used within one network to a different IP address known within another network, allowing an organization to have internal addresses that are visible internally, and external addresses that are only visible externally.

Personnel responsible for managing the network within an entity. Responsibilities typically include but are not limited to network security, installations, upgrades, maintenance and activity monitoring.

Process by which an entity’s systems are remotely checked for vulnerabilities through use of manual or automated tools. Security scans that include probing internal and external systems and reporting on services exposed to the network. Scans may identify vulnerabilities in operating systems, services, and devices that could be used by malicious individuals.

Also referred to as “segmentation” or “isolation.” Network segmentation isolates system components that store, process, or transmit cardholder data from systems that do not. Adequate network segmentation may reduce the scope of the cardholder data environment and thus reduce the scope of the PCI DSS assessment. See the Network Segmentation section in the PCI DSS Requirements and Security Assessment Procedures for guidance on using network segmentation. Network segmentation is not a PCI DSS requirement.

Refers to logical access to a system component that occurs over a network interface rather than via a direct, physical connection to the system component. Non-console access includes access from within local/internal networks as well as access from external, or remote, networks.

Software of a computer system that is responsible for the management and coordination of all activities and the sharing of computer resources. Examples of operating systems include Microsoft Windows, Mac OS, Linux and Unix.

An organizational structure that ensures there is no conflict of interest between the person or department performing the activity and the person or department assessing the activity. For example, individuals performing assessments are organizationally separate from the management of the environment being assessed.

Acronym for “Payment Application Qualified Security Assessor.” PA-QSAs are qualified by PCI SSC to assess payment applications against the PA-DSS. Refer to the PA-DSS Program Guide and PA-QSA Qualification Requirements for details about requirements for PA-QSA Companies and Employees.

In cryptography, the one-time pad is an encryption algorithm with text combined with a random key or "pad" that is as long as the plain-text and used only once. Additionally, if key is truly random, never reused, and, kept secret, the one-time pad is unbreakable

Acronym for “primary account number” and also referred to as “account number.” Unique payment card number (typically for credit or debit cards) that identifies the issuer and the particular cardholder account.

In the context of PA-DSS, a software application that stores, processes, or transmits cardholder data as part of authorization or settlement, where the payment application is sold, distributed, or licensed to third parties. Refer to PA-DSS Program Guide for details.

For purposes of PCI DSS, any payment card/device that bears the logo of the founding members of PCI SSC, which are American Express, Discover Financial Services, JCB International, MasterCard, or Visa, Inc.

Sometimes referred to as “payment gateway” or “payment service provider (PSP)”. Entity engaged by a merchant or other entity to handle payment card transactions on their behalf. While payment processors typically provide acquiring services, payment processors are not considered acquirers unless defined as such by a payment card brand. See also Acquirer.

Penetration tests attempt to identify ways to exploit vulnerabilities to circumvent or defeat the security features of system components. Penetration testing includes network and application testing as well as controls and processes around the networks and applications, and occurs from both outside the environment (external testing) and from inside the environment.

Acronym for “personal identification number.” Secret numeric password known only to the user and a system to authenticate the user to the system. The user is only granted access if the PIN the user provided matches the PIN in the system. Typical PINs are used for automated teller machines for cash advance transactions. Another type of PIN is one used in EMV chip cards where the PIN replaces the cardholder’s signature.

A block of data used to encapsulate a PIN during processing. The PIN block format defines the content of the PIN block and how it is processed to retrieve the PIN. The PIN block is composed of the PIN, the PIN length, and may contain subset of the PAN.

Acronym for “Point of Interaction,” the initial point where data is read from a card. An electronic transaction-acceptance product, a POI consists of hardware and software and is hosted in acceptance equipment to enable a cardholder to perform a card transaction. The POI may be attended or unattended. POI transactions are typically integrated circuit (chip) and/or magnetic-stripe card-based payment transactions.

Network established by an organization that uses private IP address space. Private networks are commonly designed as local area networks. Private network access from public networks should be properly protected with the use of firewalls and routers.

Any user account with greater than basic access privileges. Typically, these accounts have elevated or increased privileges with more rights than a standard user account. However, the extent of privileges across different privileged accounts can vary greatly depending on the organization, job function or role, and the technology in use.

A server that acts as an intermediary between an internal network and the Internet. For example, one function of a proxy server is to terminate or negotiate connections between internal and external connections such that each only communicates with the proxy server.

Network established and operated by a third party telecommunications provider for specific purpose of providing data transmission services for the public. Data over public networks can be intercepted, modified, and/or diverted while in transit. Examples of public networks include, but are not limited to, the Internet, wireless, and mobile technologies. See also Private Network.

Abbreviation for “Remote Authentication Dial-In User Service.” Authentication and accounting system. Checks if information such as username and password that is passed to the RADIUS server is correct, and then authorizes access to the system. This authentication method may be used with a token, smart card, etc., to provide two-factor authentication.

Access to computer networks from a remote location. Remote access connections can originate either from inside the company’s own network or from a remote location outside the company’s network. An example of technology for remote access is VPN.

Media that store digitized data and which can be easily removed and/or transported from one computer system to another. Examples of removable electronic media include CD-ROM, DVD-ROM, USB flash drives and external/portable hard drives.

Process that identifies valuable system resources and threats; quantifies loss exposures (that is, loss potential) based on estimated frequencies and costs of occurrence; and (optionally) recommends how to allocate resources to countermeasures so as to minimize total exposure.

Hardware or software that connects two or more networks. Functions as sorter and interpreter by looking at addresses and passing bits of information to proper destinations. Software routers are sometimes referred to as gateways.

The process of selecting a cross-section of a group that is representative of the entire group. Sampling may be used by assessors to reduce overall testing efforts, when it is validated that an entity has standard, centralized PCI DSS security and operational processes and controls in place. Sampling is not a PCI DSS requirement.

A set of hardware, software and firmware that implements cryptographic processes (including cryptographic algorithms and key generation) and is contained within a defined cryptographic boundary. Examples of secure cryptographic devices include host/hardware security modules (HSMs) and point-of-interaction devices (POIs) that have been validated to PCI PTS.

An occurrence considered by an organization to have potential security implications to a system or its environment. In the context of PCI DSS, security events identify suspicious or anomalous activity.

Any data center, server room or any area that houses systems that stores, processes, or transmits cardholder data. This excludes the areas where only point-of-sale terminals are present such as the cashier areas in a retail store.

Computer that provides a service to other computers, such as processing communications, file storage, or accessing a printing facility. Servers include, but are not limited to web, database, application, authentication, DNS, mail, proxy, and NTP.

Three-digit or four-digit value in the magnetic-stripe that follows the expiration date of the payment card on the track data. It is used for various things such as defining service attributes, differentiating between international and national interchange, or identifying usage restrictions.

Business entity that is not a payment brand, directly involved in the processing, storage, or transmission of cardholder data on behalf of another entity. This also includes companies that provide services that control or could impact the security of cardholder data. Examples include managed service providers that provide managed firewalls, IDS and other services as well as hosting providers and other entities. If an entity provides a service that involves only the provision of public network access—such as a telecommunications company providing just the communication link—the entity would not be considered a service provider for that service (although they may be considered a service provider for other services).

In the context of web session management, a session token (also referred to as a “session identifier” or “session ID”), is a unique identifier (such as a “cookie”) used to track a particular session between a web browser and a webserver.

Also referred to as “chip card” or “IC card (integrated circuit card).” A type of payment card that has integrated circuits embedded within. The circuits, also referred to as the “chip,” contain payment card data including but not limited to data equivalent to the magnetic-stripe data.

Form of attack on database-driven web site. A malicious individual executes unauthorized SQL commands by taking advantage of insecure code on a system connected to the Internet. SQL injection attacks are used to steal information from a database from which the data would normally not be available and/or to gain access to an organization’s host com puters through the computer that is hosting the database.

Also called “dynamic packet filtering.” Firewall capability that provides enhanced security by keeping track of the state of network connections. Programmed to distinguish legitimate packets for various connections, only packets matching an established connection will be permitted by the firewall; all others will be rejected.

Cryptography based on industry-tested and accepted algorithms, along with key lengths that provide a minimum of 112-bits of effective key strength and proper key-management practices. Cryptography is a method to protect data and includes both encryption (which is reversible) and hashing (which is “one way”; that is, not reversible). See Hashing.

At the time of publication, examples of industry-tested and accepted standards and algorithms include AES (128 bits and higher), TDES/TDEA (triple-length keys), RSA (2048 bits and higher), ECC (224 bits and higher), and DSA/D-H (2048/224 bits and higher). See the current version of NIST Special Publication 800-57 Part 1 (http://csrc.nist.gov/publications/) for more guidance on cryptographic key strengths and algorithms.

Note: The above examples are appropriate for persistent storage of cardholder data. The minimum cryptography requirements for transaction-based operations, as defined in PCI PIN and PTS, are more flexible as there are additional controls in place to reduce the level of exposure. It is recommended that all new implementations use a minimum of 128-bits of effective key strength.

Anything on a system component that is required for its operation, including but not limited to database tables, stored procedures, application executables and configuration files, system configuration files, static and shared libraries and DLLs, system executables, device drivers and device configuration files,and third-party components.

Acronym for “Terminal Access Controller Access Control System.” Remote authentication protocol commonly used in networks that communicates between a remote access server and an authentication server to determine user access rights to the network. This authentication method may be used with a token, smart card, etc., to provide two-factor authentication.

Condition or activity that has the potential to cause information or information processing resources to be intentionally or accidentally lost, modified, exposed, made inaccessible, or otherwise affected to the detriment of the organization.

In the context of authentication and access control, a token is a value provided by hardware or software that works with an authentication server or VPN to perform dynamic or two-factor authentication. See RADIUS, TACACS, and VPN.

Also referred to as “full track data”or “magnetic-stripe data.” Data encoded in the magnetic stripe or chip used for authentication and/or authorization during payment transactions. Can be the magnetic-stripe image on a chip or the data on the track 1 and/or track 2 portion of the magnetic stripe.

Also referred to as “Trojan horse.” A type of malicious software that when installed, allows a user to perform a normal function while the Trojan performs malicious functions to the computer system without the user’s knowledge.

Method of rendering the full PAN unreadable by permanently removing a segment of PAN data. Truncation relates to protection of PAN when stored in files, databases, etc. See Masking for protection of PAN when displayed on screens, paper receipts, etc.

A process of assigning version schemes to uniquely identify a particular state of an application or software. These schemes follow a version-number format, version-number usage, and any wildcard element as defined by the software vendor. Version numbers are generally assigned in increasing order and correspond to a particular change in the software.

A VA takes the concept of a pre-configured device for performing a specific set of functions and run this device as a workload. Often, an existing network device is virtualized to run as a virtual appliance, such as a router, switch, or firewall.

The VMM is included with the hypervisor and is software that implements virtual machine hardware abstraction. It manages the system‹s processor, memory, and other resources to allocate what each guest operating system requires.

A virtual switch or router is a logical entity that presents network infrastructure level data routing and switching functionality. A virtual switch is an integral part of a virtualized server platform such as a hypervisor driver, module, or plug-in.

Virtualization refers to the logical abstraction of computing resources from physical constraints. One common abstraction is referred to as virtual machines or VMs, which takes the content of a physical machine and allows it to operate on different physical hardware and/or along with other virtual machines on the same physical hardware. In addition to VMs, virtualization can be performed on many other computing resources, including applications, desktops, networks, and storage.

Acronym for “virtual private network.” A computer network in which some of connections are virtual circuits within some larger network, such as the Internet, instead of direct connections by physical wires. The end points of the virtual network are said to be tunneled through the larger network when this is the case. While a common application consists of secure communications through the public Internet, a VPN may or may not have strong security features such as authentication or content encryption. A VPN may be used with a token, smart card, etc., to provide two-factor authentication.

Acronym for “Wired Equivalent Privacy.” Weak algorithm used to encrypt wireless networks. Several serious weaknesses have been identified by industry experts such that a WEP connection can be cracked with readily available software within minutes. See WPA.

A character that may be substituted for a defined subset of possible characters in an application version scheme. In the context of PA-DSS, wildcards can optionally be used to represent a non-security impacting change. A wildcard is the only variable element of the vendor’s version scheme, and is used to indicate there are only minor, non-security-impacting changes between each version represented by the wildcard element.

Also referred to as “AP.” Device that allows wireless communication devices to connect to a wireless network. Usually connected to a wired network, it can relay data between wireless devices and wired devices on the network.

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